From af8cd71f59c54f4b7d402aaa2e798cffbc308b1e Mon Sep 17 00:00:00 2001
From: Amoelle <amoelle@proton.me>
Date: Sun, 25 May 2025 14:30:03 +0300
Subject: [PATCH] create simple kernel in C with a linker script

---
 kernel.c  | 29 +++++++++++++++++++++++++++++
 kernel.ld | 29 +++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)
 create mode 100644 kernel.c
 create mode 100644 kernel.ld

diff --git a/kernel.c b/kernel.c
new file mode 100644
index 0000000..6abe1b7
--- /dev/null
+++ b/kernel.c
@@ -0,0 +1,29 @@
+typedef unsigned char uint8_t;
+typedef unsigned int uint32_t;
+typedef uint32_t size_t;
+
+extern char __bss[], __bss_end[], __stack_top[];
+
+void *memset(void *buf, char c, size_t n) {
+    uint8_t *p = (uint8_t *) buf;
+    while (n--)
+        *p++ = c;
+    return buf;
+}
+
+void kernel_main(void) {
+    memset(__bss, 0, (size_t) __bss_end - (size_t) __bss);
+    
+    for (;;);
+}
+
+__attribute__((section(".text.boot")))
+__attribute__((naked))
+void boot(void) {
+    __asm__ __volatile__(
+        "mv sp, %[stack_top]\n" // Set stacker point
+        "j kernel_main\n"       // Jump to the kernel function
+        :
+        : [stack_top] "r" (__stack_top) // Pass the stack top address as %[stack_top]
+    );
+}
diff --git a/kernel.ld b/kernel.ld
new file mode 100644
index 0000000..d545dda
--- /dev/null
+++ b/kernel.ld
@@ -0,0 +1,29 @@
+ENTRY(BOOT)
+
+SECTIONS {
+    . = 0x80200000;
+
+    .text :{
+        KEEP(*(.text.boot));
+        *(.text .text.*);
+    }
+
+    .rodata : ALIGN(4) {
+        *(.rodata .rodata.*);
+    }
+
+    .data : ALIGN(4) {
+        *(.data .data.*);
+    }
+
+    .bss : ALIGN(4) {
+        __bss = .;
+        *(.bss .bss.* .sbss .sbss.*);
+        __bss_end = .;
+    }
+
+    . = ALIGN(4);
+    . += 128 * 1024 /* 128KB */
+    __stack_top = .;
+
+}